JOHANNESBURG (AP) - Soldiers in Cameroon are losing the battle to save the last elephants in a remote frontier park from marauding horsemen believed to be invading from Sudan, the World Wildlife Fund said Thursday.

'The forces arrived too late to save most of the park's elephants, and were too few to deter the poachers,' said Natasha Kofoworola Quist, director of the fund's Central Africa program. 'WWF is disturbed by reports that the poaching continues unabated in Bouba N'Djida National Park and that a soldier's life has been lost.'

She said at least half of the park's 400 elephants have been killed.

David Hoyle, the fund's conservation director in Cameroon, said the government had sent up to 150 soldiers into the national park on March 1—taking action after weeks of pressure from the fund and from the European Union.

Hoyle said at least another 20 elephants were slaughtered during the first week of the military deployment.

'We know there have been confrontations between the military and the poachers, we don't have figures on how many have been arrested or killed,' he said.

This past year has seen an unprecedented increase in poaching of elephants for their tusks which are smuggled mainly to China and Thailand to make ivory ornaments.

Wildlife activists blame China's growing footprint in Africa for an unprecedented surge in poaching elephants for their tusks. Most are believed to be smuggled to China and Thailand to make ivory ornaments.

Growing demand for ivory in China is 'the leading driver behind the illegal trade in ivory today,' said Tom Milliken, an elephant and rhino expert for the wildlife trade monitoring network TRAFFIC. China has a legal ivory market that is supposed to be highly controlled but tons and tons of illegal ivory has made its way there in recent years, said the Zimbabwe-based Milliken, who spoke in a conference call with several World Wildlife Fund officers.

Chinese middlemen among new immigrants to Africa have 'cornered the market' for poached ivory, offering prices that have put thousands of Central African ivory carvers out of work.

Ivory sales are banned in most countries since the 1980s under an international treaty to help conserve elephants.

Kofoworola Quist said the World Wildlife Fund has for years been warning Cameroon that its game rangers are not properly trained or equipped to address the scale, intensity and organized nature of the poaching.

Heavily armed poachers are believed to come from Sudan and Chad, moving on horseback with herds of cattle and camels and sometimes crossing through Central African Republic.

'They move 1,000 kilometers (more than 600 miles) on horseback to get to northern Cameroon because they have already wiped out the elephants of Chad and Central African Republic,' said Richard Carroll, vice president of the U.S. chapter of WWF.

Quist said the fund wants 'a concrete assurance' from Cameroon's President Paul Biya 'that he will do whatever is necessary to protect the remaining elephants in Bouba N'Djida, and to bring the killers to justice.'

The fund had urged Cameroon to engage the governments of Chad and Sudan in a coordinated response.

'WWF has offered its assistance and is awaiting meaningful action from Cameroon and its neighbors,' she said.

Northern Cameroon's elephant population represents 80 percent of the total population of savanna elephants in all of Central Africa.